1. The Field of the Invention
The present invention relates generally to systems and methods for delivering electronic messages. More particularly, embodiments of the invention relate to allowing challenge messages from federated messaging services to be delivered directly to a recipient's inbox if the challenge message is authenticated and validated.
2. Relevant Technology
Electronic messaging or e-mail has become, for many people, a primary means of communication. The ease by which a person is able to send and receive an electronic message makes this form of communication extremely attractive. Unfortunately, others utilize electronic messaging to send unsolicited bulk electronic messages, better known as “spam.” Unsolicited electronic messages may include commercial advertisements, political messaging, as well as pornographic solicitations. Due to the influx of unsolicited electronic messages, people have become wary of giving out their electronic addresses for fear that their address will be sold to would-be solicitors. Further, those who receive spam are often not able to successfuilly request removal from mass e-mailing lists. Moreover, it is difficult to ascertain who has sent unsolicited electronic messages, since solicitors often use fabricated addresses or refrain from including one altogether.
Challenge and response mechanisms have been developed as a way to filter out unwanted electronic messages. When an electronic message is directed to a recipient, the message is delivered to the recipient only if the sender is identified as being authorized to send electronic messages to the recipient. Usually, the recipient has a list of approved senders, allowing the electronic message from the approved senders to be sent to the recipient's inbox without a challenge.
However, when the sender is unknown, a challenge message is sent to the sender to verify that the sender's address is valid and that the sender is a person as opposed to a machine before delivering the senders email to the recipient's inbox. The sender is confirmed by asking the sender to respond to the challenge message in a way that affirmatively verifies that the sender is a person as opposed to a machine. This challenge/response method is quite successful in eliminating unsolicited electronic messages that are sent by mass-mailers.
However, challenge/response systems are based on a set of rules that do not take into consideration certain scenarios in which a recipient would actually like to receive an incoming message. In these situations, the challenge/response system is overinclusive, meaning that the spam protection actually prevents wanted messages from being sent directly to the recipient. FIGS. 1A and lB illustrate two such scenarios.
In one example, shown in FIG. 1A, user A sends an original message from service A to user B associated with service B, the original messaging being addressed TO beta@serviceB.com and FROM alpha@serviceA.com. Assuming this is the first time that user B has received an electronic message from user A, service B will generate a challenge message. The server generating the challenge message, in some cases, will place in the FROM field the identity of the server, resulting in a challenge message being addressed TO alpha@serviceA.com and FROM postmaster@serviceB.com. Because service A will likely not recognize the address in the FROM field of the challenge message, service A will send the incoming challenge message to user A's pending folder and user A will not have the opportunity to reply.
Furthermore, if service A utilizes a challenge/response mechanism, service A will issue a second challenge in response to the incoming first challenge message containing the unknown address (i.e., postmaster@serviceB.com). The second challenge sent to service B may result in yet another challenge being sent to service A. Meanwhile, the original message from user A remains undelivered to user B at user B's server. Appreciably, a “challenge war” has been created in which multiple challenges are sent to both parties, and neither party is aware of the existence of an original message and/or challenge message.
In another example, shown in FIG. 1B, user A associated with messaging service A sends an original message to user B associated with messaging service B, the original messaging being addressed TO beta@serviceB.com and FROM alpha@serviceA.com. Suppose user B's service B then forwards the message to user B's remote account user B1 associated with service C. With some forwarding mechanisms, the forwarding protocol creates an electronic message in which the FROM field uses the address of the original sender. Thus, a forwarded message may be addressed TO beta 1 remote@serviceC.com and FROM alpha@serviceA.com. Assuming this is the first time service C has received a message from user A, service C send a challenge message to user A. Thus, a challenge message from service C will be addressed TO alpha@serviceA.com from beta 1 remote@serviceC.com or postmastereserviceC.com. The challenge message will be sent to A's pending folder since the FROM address is unknown and the original message left undelivered to user B1.
Further, service A could send a subsequent challenge message to service C if it does not recognize the FROM address. However, because service C is unfamiliar with user A's address, the challenge message is sent to user B1's pending folder. Thus, both user A and user B1 will have challenge messages in their pending folders, but will not be aware of them or may become aware of them after the time for responding to the challenge message has expired. Furthermore, repeated attempts by user A to send messages to user B will continue to result in additional challenges by both services A and C, which creates a “challenge war” situation in which both parties are sending challenges and yet neither party is aware of the incoming challenges, while, in reality, it is likely that user A and user B1 would not consider messages from each other as spam.
Thus, conventional challenge and response filtering systems are overinclusive and present users from receiving desired challenge messages in situations where the user would actually like to receive the message. It would be advantageous to provide message filtering systems that are capable of delivering such electronic messages without issuing a challenge message or otherwise failing to deliver the messages.